Iodination of mouse EGF with chloramine T at 4 degrees C: characterization of the iodinated peptide and comparison with other labelling methods.

A modified Chloramine T labelling procedure was used to iodinate mEGF in order to perform radio-receptor assays. The reaction was conducted at 4 degrees C with 1 mu g Chloramine T only. The tracer obtained was characterized by its maximal binding, specific activity and binding properties compared with the native peptide. Fast Liquid Protein Chromatography was performed to analyse the homogeneity of the preparation and membrane extracts from A431 cells were used to purify the tracer. The modified Chloramine T procedure was compared with two other methods: the classical Chloramine T iodination and the labelling procedure using Enzymobeads. The modified Chloramine T procedure is reproducible, provides labelled mEGF with high binding capacity (65 to 80% with canine placental membrane extracts) and high specific activity (351 +/- 107 mu Ci/mu g mEGF) and seems to preserve the binding properties of the native peptide.